Now that we can officially add themes to Microsoft Edge browser in Canary channel (soon in all channels), I think we should have some themes in Microsoft's own Addons store which is this:
https://microsoftedge.microsoft.com/addons/category/Edge-Extensions
and we shouldn't have to go to chrome store to download themes for Edge browsers.
specially after they show these fake banners saying Edge is not safe to use extensions on.
https://techcommunity.microsoft.com/t5/discussions/google-is-incompetent/td-p/1197965
plus, I think Microsoft can come up with some interesting designs for the Edge browser 
I completely agree.
Themes matter a lot to people who like to personalise their software. I am sure Microsoft is working on adding themes to the Microsoft Edge Add-ons store. I hope they will allow third-party themes to be uploaded as well, so that there is a greater range to choose from.
Themes can be installed from the Chrome Webstore as well. However, not every user enables installation from third-party stores. So, it will be great to have access to themes on the official add-ons store.
I also feel that the experience on downloading themes from the Chrome Webstore is buggy sometimes: for example, the title color is frequently wrong. So, I believe that Microsoft should also work on improving support for themes from Chrome Webstore. This will have twin-benefits, because then, many themes from there can simply be ported to the Edge Add-ons store as well.
And lastly, I really want the ability to change the shape of the omnibox (URL bar), tabs etc. This will lift the experience to a whole new level because all we can do with themes at present is to change the color of a few UI elements of the browser.
I also hope that taking the above suggestion into consideration, Microsoft publishes an "Edge Legacy theme".